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JB welder
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Discussion Starter #1
So, it all started about a month ago. Temperature was around 30°F. I had never had a problem with my truck before then, but this particular evening I was leaving work after a 10 hour shift and when I tried to start my old 97 I got nothing. I later determined it was the starter and replaced it with a brand new one. Then I found out my batteries were bad. Replaced them. Then after cranking on and off for about an hour I decided that starting fluid was my only option. I sprayed a but in the intake hose and bingo it fired right up. Since that day my truck has never started without first being plugged in. The oil cooler seals went bad and I started leaking a fair amount of oil so I had it towed home and began a slight overhaul. I replaced- the glow plug relay, valve cover gaskets and both inner and outer wiring harnesses, crank position sensor, icp, fuel filter, downpipe, oil cooler seals, oil dipstick O ring and of course fresh oil and anti freeze.
The fuel is fine and I've used additive to prevent gelling, the glow plugs were replaced by previous owner, about 2000 miles ago. Truck runs fine when it runs and when cranking and unplugged I get a descent amount of white smoke. Any help would be great. Btw about three months ago I had a buddy read codes and it said I need a new idm, could this be the issue?

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What brand of glow plugs? What brand of GP relay? Have you TESTED them? The fact that you didn't blow something up using starting fluid suggests that they're not working.

When you don't plug it in, how long do you leave the key in RUN before turning it to START? How long does the WTS light stay on?
 

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JB welder
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Discussion Starter #3
Not sure of brand, but I'm sure they were the cheapest available. Gpr was duralast. I tested it and it was good. Haven't tested glow plugs, how is that done. I usually wait about 30 seconds after turning key to try and start truck. The wts light stays on about 20 seconds when it's cold and about 7 seconds after the truck is warm and has been ran recently.

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Measure the resistance of the glow plugs at the UVCH connector. Outermost pins of each connector. Should be about 1 ohm each. If they're Autolites, get them out of there; they'll swell up over time and can become a PITA or impossible to remove. Motorcraft/Beru ZD-11 are the only ones to be trusted, affordable at aprx. $80 a set.

FLAPS relay won't last. Just because it's "clicking" doesn't mean it's providing sufficient voltage to the GPs. Measure the voltage at each of the big terminals WHILE it's active (right after turning the key to RUN). The "always hot" one will usu. be higher than the one going to the glow plugs, but if the _difference_ is more than 0.3V, the relay is weak.
 

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JB welder
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Discussion Starter #5
I'll measure the resistance of the gps and check the voltage of the relay. I'm probably gonna change out the glow plugs either this weekend or next weekend regardless, if the autolites are really that bad then I'm not gonna chance it because I'm not sure of brand

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JB welder
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Discussion Starter #7
Well, I checked my glow plug relay and gps with my new multimeter. The relay seemed to read good with 12.32 volts on the hot side and 0.0 volts on the keyed side while the key was off. With the key "on" the keyed side of the relay reads 12.03 volts and the constant "hot" side reads 12.25 volts. The keyed side reads over 12v steady for about 45 seconds.

Gp test showed some weird results. Passenger side closest to the firewall read 2.0 ohms and the rest read "O.L."but I don't know what that means?! All but one of the glow plugs on the drivers side read "O.L." Except one and it read 73 ohms or something crazy like that.

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That "O.L." means infinite resistance. The equivalent to a burned out light bulb - open circuit. Those GPs are therefore inop. Now you get to find out if it's because of an interruption in the connection from the UVCH connector to the glow plugs, or if it's the glow plugs themselves. IOW, time to pull the valve covers and chase the open circuit(s) down further.

That also explains the voltage. With all eight GPs running, the load should pull the voltage down to about 11.5. Since you have some inop glow plugs, you have less load, and therefore the less loss of voltage.

Relay itself does read good. But you'll know more for certain doing the same voltage tests with eight good glow plugs actually loading on it.
 

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JB welder
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Discussion Starter #9
UVCH's were changed last Sunday along with the outer pig tails and the gaskets, I rechecked them today and all looked perfect!

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So you checked the wiring on all eight, from the gaskets to the glow plugs themselves? If that's all good, next step is to confirm inop glow plugs by measuring resistance right at the terminal on each GP.
 

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JB welder
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Discussion Starter #12
I hate when people don't post what the problem actually was so here goes. I replaced all if my glow plugs this weekend, I was pretty scared when I saw the first one was an autolite but thankfully they all came out no problem. Two of the glow plugs looked really burnt up but the rest all looked like new. After installing the new motorcraft ZF-11's the old 7.3 started right up and has started just fine since and it's been around 10°f

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simple test for gp s tester positive side of battery to plug connector for each gp if it lights gp is junk no light is good done this and it works with no confusion
 

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simple test for gp s tester positive side of battery to plug connector for each gp if it lights gp is junk no light is good done this and it works with no confusion
And....youve got that backwards. otherwise.... it is a good quick test and use it all the time.
 
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